Selective signaling



PATBNTEDPBB. 2s, 1904-. R. A, PESSENDEN.'

Y SELECTIVE SIGNALING.

NG MODELA APBLIGATION FILED DEG. 29, 1902.

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PATENTEB FEB. 23,l 1904.

R. A. PESSEN'DBN. SELEGTIVB SIGNALING. APPLICATION FILED DEO. 29, 1902.

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uwen-ron (Kimm/UM M Mw WITNESSES UNITEDSTATES Patented February 23,1904.

PATENT OFFICE.

REGINALD A. FESSENDEN, OF FORTr MONROE, VIRGINIA, ASSIGNOR, BY y DIRECTAND MESNE ASSIGNMENTS, TO THE NATIONAL ELECTRIC SIG- NALING COMPANY, OFlPITTSBURG, PENNSYLVANIA, A CORPORATION OF NEW JERSEY.

SELECTIVE SIGNALING. A

SPECIFICATION forming part of Letters Patent No. 752,894, dated February23, 1904.

l Application led December 29, 1902. Serial No. 136,98. (No model.)

To LEZ whom, t may concern."

Be it known that'I, REGINALD A. Fassun- DEN,`a citizen of the UnitedStates, resid ing at Fort Monroe, in the county of Elizabeth City andState yof Virginia, have invented or discovered certain new and usefulImprovements in Selective Signaling, of which improvements' .I 5stations being cut out or non-responsive, and

also to securing freedom from disturbing iniiuences during signaling. Inthe methods heretofore employed freedom from disturbances andselectivity have been secured by 2O electrically tuning the sending andreceiving apparatus at the different stations, each station having aseparate electrical tune. This method, while efficient for a great manypurposes, requires a great deal of care in its operation and theadjustment of the mechanism in maintaining the stations in tune. l Abetter selectivity and greater freedom from disturbances can be obtainedby mechanical tuning or mechanical and electrical tuning.

The invention is hereinafter more fully described and claimed.

In the accompanying drawings, forming a part of this specification,Figure l is a diagrammatic view illustrating a desirable form ofapparatus and circuits A.for the sending and receiving stations. Figs. 2and 3 illustrate modifications in the form of apparatus and circuits forreceiving stations, Fig. 3 also including a sending-station; and Fig.Liis another form of selective receiving-circuits.

In the practice of my invention electromagnetic waves are generated witha certain predetermined frequency-as, for example, two million persecond-in groups which have a frequency diiferent from the frequency ofthe waves composing said groups-as, for example, a frequency of onehundred and twentysix (126) per second. Any suitable form ofconstruction of apparatus maybe employed for thus generating theelectromagnetic V'waves 'in groups-as, for example, an induction-coilhavingv a spark-gap connected in the' usual manner and a make-'and-breakmechanism for the induction-coil actuated by a tuning-fork or Vothersuitable means operative at a `rate corfrequency, so that unless theindicating mechanism-e. g., the tuning-fork or telephone at thereceiVing-station-is tuned to the group frequency no indications orsignals will be produced at the receiving-station. y

In the construction shown in Fig. l the vertical wire l is connected toone terminal of the spark-gap 2, the opposite terminal thereof beinggrounded. Both terminals of the spark-gap are connected to the terminalsof the secondary of an induction-ccd3, and in the primary circuit of theinduction-coil is included a tuning-fork make-and-break mechanism, whichis operated by a local circuit, so as to vibrate by preferencecontinuously.

As shown in Fig. l, the prongs aand e of the tuning-fork i are arrangedon opposite sides of an electromagnet 21, having one terminal connectedto a battery 22 and the other terminal to the prong c, to which issecured a flexible spring 23 in such manner as to make and break contactwith the stationary contact 24 as the prong vibrates, said contact beingconnected to the otherterminal of the battery 22. The primary circuit ofthe induction-coil 3 includes the prong, carryinga contact-point 25, astationary contact-point 26, and a battery 27. By closing the key 5 inthe primary of the induction-coil sparks will be produced at thesparkgap at the rate of one hundred and twenty-six (126) per second, andas long as the key 5 is kept closed the primary circuit of theinduction-coil Will be closed, and the induction-coil Will operate toproduce a spark at the spark-gap every time the circuit is broken andcompleted by the the tuning-fork makeand-break mechanism. As each sparkcauses a group of electromagnetic Waves to be generated, it is evidentth at there will be one hundred and twenty-six (126) such groups ofelectromagnetic Waves generated and radiated per second. At thereceiving-station a Wave-responsive devicev 7 is arranged in series Withthe receiving-Wire 6, such Wave-responsive device being preferably abarretter, such as described and claimed in Patent No. 706,7 44,.

granted to me August 12, 1902. Atelephone 8, having a tongue 9 inplaceof a diaphragm and tuned so as to respond to one'hundred andtwenty-six (126) vibrations per second, is

connected in the circuit of the barretter, said circuit also including abattery 10. Aresistance 11 is so arranged in the circuit as to balancethe normal resistance of the barretter.

Normally the tongue of the telephone -Will not vibrate; but as soon ascurrents are generated by the electromagnetic Waves in the receiving-Wire the resistance of the barretter is changed, vand if proper currentshave been generated the tongue 9 Will be caused to vibrate.

In the construction shovvn in Fig. 2 and in lieu of a telephone having avibrating tongue an ordinary telephone 12 is employed, and the circuitincluding this telephone is tuned electrically, by means of theinductance 13 and capacity 14,'to respond to a group frequency, such asis generated at the sending-station. It is preferred to combineelectrical tuning to group. frequency with mechanical tuning to -groupfrequency. A suitable method of` accomplishing this result is shown inFig. 4, Where the vertical receiving-conductor 6 is connected to groundand includes in series therewith a barretter 7, which is also in seriesWith a secondary circuit electrically tuned to the group frequency andcontains a battery, an'inductance, a capacity, and a telephone 28,having a tongue tuned mechanically to the group frequency. In thisarrangement, the local or secondary circuit being tuned electrically andthe mechanism 28 tuned mechanically,

the selection is more pronounced. In practice itis found thata change ofless than one-fifth of one per cent. in the group frequency Will cause achange from maximum audibility to complete silence.

In addition to tuning to group frequencies I may also tune to Wavefrequencies,and in such case I prefer to employ an auxiliary circuit 28at the sending-station, such as that shown in Fig. 3, said circuitoperating in a manner Well known in the art and fully described inLetters Patent No. 706,735, granted to me August 12, 1902, to prolongthe electrical oscillations and permit of a sharp electrical tuning. Atthe receiving-station the Wave-responsive device, as the barretter 7, ispreferably placed in the circuit of the secondary of a transformer 15,the primary of said transformer being in series with thereceiving-conductor. In the same circuit is included the primary of asecond transformer 16 and a local battery. In the circuit of thesecondary of this second transformer 16 is included a loop 17,preferably formed of silver or phosphor-bronze rolled out into a stripand arranged in a strong magnetic field produced by a permanent magnet18. This loop is connected toone terminal of the indicating-circuitcontaining the indicating device 20 and is so arranged that when causedto vibrate it Will make contact With the other terminal 19 of theindicating-circuit, .closing the latter. On Waves being received alcurrent is generated inthe secondary of the first transformer whichalters the resistance of the barretter or Wave-responsive device,causing a change of current in the primary of the second transformer.This causes a current in the secondary of the latter transformer, saidsecondary having, by preference, fewer -turns than the primary, socausing the loop to vibrate andV make or break the indicating-circuit,including the indicating or recording device 20. Where electrical tuningis used in addition to mechanical tuning, it is preferred that all thegroups of stations Which are intended to communicate with each othershould be tuned to the same Wave frequency, but to different groupfrequencies.

In many cases it is preferable to combine all three methods hereindescribed-fc'. e. a receiving-station .having one circuit tunedelectrically to the Wave frequency, one circuit tuned electrically tothe group frequency, and a mechanism tuned mechanically to the groupfrequency. Such a construction is shown in Fig. 4, `Where thereceiving-conductor 6 is tuned electrically to the Wave frequency, thesecondary circuit is tuned electrically to the group frequency, and themechanism 28, consisting of a telephone With tuned tongue, is tunedmechanically to the group frequency.

While the constructions herein described are suitable and for manypurposes desirable, the invention is not limited to the particular formsor constructions shown; but any suitable form or construction wherebyelectromagnetic Waves are generated in any desired group frequency andsuch Waves are operative at the receiving-station to produceintelligible indications or signals Vmay be employed-as, for example, anapparatus substantially similar to that shown in Fig. 10 of LettersPatent No. 706,742, granted to me August 12, 1 902, may lbe'used forgenerating electromagnetic Waves IOO at the desired group frequency, andat the receiving-station I may employ apparatus substantially as thatshown and described in Fig. 8 of said patent.

By the term mechanical frequencies as used herein is meant frequenciessuch as are found in or dealt with in mechanical problems, and moreespecially such frequencies as are concerned With the production ofmusical notes.

I claim herein as my invention 1. As an improvement in the artof'signaling by electromagnetic Waves the method described herein whichconsists in generating electrical oscillations at arsending-station,radiating prolonged series of electromagnetic Waves from thesending-station, in groups of apredetermined frequency lower than thefrequency of the waves forming said groups, receiving said Waves at areceiving-station, and producing indicationsor signals at thereceiving-station by selecting groups of the predetermined frequency,substantially as set forth.

2. As an improvement in the art of signaling by electromagnetic Wavesthe method described herein Which consists in generating electricaloscillations at a sending-station, radiating prolonged series ofelectromagnetic Waves from the sending-station, in groups of apredetermined frequency lower than the frequency of the Waves formingsaid groups, receiving said Waves at a receiving-station on acurrent-operated receiver, and producing indications or signals at thereceiving-station by selecting groups of the predetermined frequency,substantially as set forth.

3. As an improvement in the art of signaling by electromagnetic Wavesthe method described herein Which consists of producing prolongedelectrical oscillation in an auxiliary circuit at a sending-station,radiating prolonged series of electromagnetic Waves from thesending-station, in groups of a predetermined frequency lower than thefrequency of the Waves forming said groups, receiving said Waves at areceiving-station, and producing indications or signals at thereceiving-station by selecting groups of the predetermined frequency,substantially as set forth.

4. As an improvement in the art of signaling by electromagnetic Wavesthe method described herein Which consists in. generating electricaloscillations at a sending-station, radiating prolonged series ofelectromagnetic Waves from the sending tation, in groups of apredetermined freq/uey lower than the frequency of theWaves forming saidgroups, re- Ceiving said Waves at a receiving-station tuned to thefrequency of the electrical Waves, and producing indications or signalsat the receiving-station.

5. As an improvement in the art of signaling by electromagnetic Wavesthe method described herein Which consists of producing prolongedelectrical oscillations in 4an auxiliary circuit at a sending-station,radiating prolonged series yof electromagnetic Waves from thesending-station, in groups of a predetermined frequency loWer than thefrequency of the Waves forming said groups, receiving said Waves at areceiving-station tuned to the frequency of the Waves,'and producingindications or signals at the receiving-station byselecting groups ofthe predetermined frequency, substantially as set forth. Y

6. As an improvement in the art of signaling by electromagnetic waves,the method herein described which consists in generating electromagneticWaves of a predetermined frequency in groups of a predetermined groupfrequency lower than that of the Waves and producing signals orindications at the receiving-station by selecting electrically Waves ofa predetermined Wave frequency, and selecting mechanically groups formedof such electrically-selected Waves and lof the predetermined frequency,substantially as set forth.

In testimony whereof I have hereunto set my hand.

REGINALD A. FESSENDEN.

Witnesses:

R. Gr. BAILEY, T. L. SCLATER.

